TrainingPeaks, aerobic decoupling (Pa:HR / Pw:HR)

Practitioner method for quantifying cardiovascular drift as a field measure of aerobic durability: compare the pace-to-heart-rate (or power-to-heart-rate) ratio in the first half of a steady effort with the second half. A commonly used interpretive scheme treats under 5% as good aerobic endurance, 5-10% as moderate, over 10% as a sign of insufficient base; the thresholds are a convention, not a physiological rule. Practitioner reference, not peer-reviewed.